Cold-shrink articles are used in a variety of applications including, for example, splicing together lengths of cable and protecting, sealing, and/or insulating spliced portions of the cable from adverse environmental conditions. A cold-shrink article generally refers to a member that is capable of being expanded and mounted in an expanded state on a removable support core. The support core is typically hollow to allow the support core and mounted cold-shrink article to be fed over a substrate. The support core is typically designed to collapse or otherwise be removed on demand and thereby allow the cold-shrink article to shrink from its expanded state into contact with a substrate positioned inside the support core. For a given application, a cold-shrink article is typically selected that, when released from the core in the absence of a substrate, will shrink from the expanded state on the core to a relaxed state having an inner diameter smaller than the outer diameter of the intended substrate. When deployed on the substrate, such sizing prevents the cold-shrink article from fully relaxing from the expanded state, which ensures a snug and resilient engagement between the cold-shrink article and the substrate. Once the cold-shrink article is conveyed onto the substrate, the cold-shrink article remains in a partially expanded state over the life of its engagement with the substrate.
Some constructions of electrical cables, particularly early constructions of cables intended for underground use, consist of a lead jacket surrounding one or more electrical conductors, with a layer of insulative, oil-impregnated paper placed between the lead jacket and the electrical conductors. Cables of this construction are commonly referred to as paper-insulated lead-covered cables (“PILC cables”). Although modern cables now have extruded dielectric (plastic) jackets with no fluid inside, there are still substantial amounts of PILC cables in use. When a PILC cable needs to be repaired, terminated, or spliced, a seal (often referred to as an “oil-stop”) must be provided to contain fluid in the cable system, due to the deleterious effects caused by the egress of the oil or other dielectric fluid used. Fluid in the cable system is often under pressure due to thermal expansion of the fluid from energy dissipated by the energized cable, and the pressure often fluctuates as the internal temperature of the cable changes due to, for example, changing energy loads.
There are several different types of systems for providing an oil-stop in PILC cables. Some sealing systems install combinations of mastic or resin and tape or heat-shrink tubes over the cable. A problem with these solutions is that the seal does not expand and contract sufficiently with the thermal expansion and contraction of the cable (and the associated changes in oil pressure) and therefore tends to leak oil after some years in service. Other solutions use an elastomeric material (such as a rubber tube or rubber tape) covered with a restricting tape or compound that doesn't stretch. The restrictive cover prevents swelling of the elastomer as oil diffuses into the material, and thereby limits the amount of oil that can diffuse into the elastomer. The available systems for providing an oil-stop are also disadvantageous in that their installation is very labor intensive, the quality of the seal is sensitive to the skill of the installer, and the installation sometimes requires the handling of chemicals and/or heat sources in the field.